1. Field of the Invention
The present invention relates to a packaging body for heating processing capable of preventing from bursting the packaging body by the internal rising pressure due to heating as well as the contents of food or the like can be cooked by heating as it is packaged in a packaging body filled with food or the like.
2. Description of the Related Art
Conventionally, many kinds of packaged foods which are already cooked or half-cooked, filled in a plastic packaging bag having heat resistance and cooked by heating using a microwave oven immediately before eating are provided in the market.
Then, when these packaged foods are heated by a microwave oven, the internal pressure rises by thermal expansion of water evaporation of the internal bag and internal air, then at last, the bag bursts, the contents are scattered and the internal of the microwave oven is polluted, therefore, some sort of means are taken to these bags in order to prevent the occurrence of the foregoing defaults.
For example, when the foregoing internal pressure rises to more than a certain level, a vapor communication means by which one portion of a heat seal is peeled off so as to release the pressure is known.
However, surrounding heat seal portions for fabricating a bag are joined together with a high heat seal strength in order to tightly and securely seal and package the contents without easily being peeled off. On the other hand, the foregoing vapor communication heat seal portion is configured so that it is comparatively easily peeled off by the internal pressure generated during the heat-cooking process. Thus, in the heat seal portions, both heat seal strengths are differently set respectively, that is, the heat seal portion which allows the vapor to eject outwardly by the internal bag pressure is fabricated as a portion having a weak heat seal strength than those of the surrounding heat seal portions for fabricating a bag.
Therefore, at the time when the bag is fabricated or filled with the contents and packaged, in order to set the foregoing different heat seat strengths, the configuration of the foregoing vapor communication heat seal portion is formed by using a complex polyolefinic resin or the like for a sealant layer which is to be an easy-open-film as a plastic film base material of the bag.
Due to the work, the configuration of the bag has been too complex and troublesome, and in addition, the manufacturing cost has been raised at the time when a bag is fabricated or filled with the contents and tightly packaged, thereby not being easily capable of providing packaged foods or the like to the market at a lower cost.